This morning, the 15th September, after 20 years
in space, Cassini ended her mission exploring the Jovian and Saturnian systems,
intentionally vapourising itself by crashing into the atmosphere of Saturn. Due
to the huge distance they had to be relayed, signals of the data collected right
up until the moment of destruction took several hours to reach Earth.
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| Artistic visualisation of Cassini starting her final plunge towards Saturn (Credit: NASA) |
The death of Cassini was of utmost importance for the
Planetary Protection of the outer solar system (see PPOSS.org). The more Cassini’s observations
have taught us about the icy moons of Saturn and Jupiter, the more we have
realised just how complex, interesting and important these extraterrestrial
worlds are.
Enceladus, Europa and Ganymede are all now known to contain
vast internal water oceans under a protective icy shell, Titan has a complex
atmosphere full of organic molecules and lakes of hydrocarbons on its surface.
There is a chance that these environments may harbour life or at least have
complex systems of pre-biotic chemistry. In this respect Cassini created more
questions than it answered, creating massive interest in further exploration of
these bodies, with specific life detection missions.
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| Cassini discovered Enceladus has a subsurface ocean and water vapour plumes which contain organic matter and evidence of water-rock interactions - the building blocks and a potential energy source for life (Credit: NASA) |
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| Cassini saw through Titan's thick hazy atmosphere to discover a hugely complex world with hydrocarbon lakes, methane rain and active geology (Credit: NASA) |
In order for future missions to study these questions, we
must not contaminate these bodies with terrestrial microbes or organic
contaminants which may accidentally be detected and mistaken for indigenous
alien life. This is where planetary protection comes in. Cassini was dirty, not
having undergone strict contamination control cleaning procedures and so will have
been carrying an unfortunate payload of microbes and organic molecules. If
Cassini had been allowed to continue its orbit around Saturn unchecked, its
orbit could have decayed over time leading to a crash landing on one of the
moons which may have led to uncontainable and irreversible contamination.
Cassini’s fiery death therefore saves the pristine conditions
on these fascinating moons for future generations of scientists to explore.
Goodbye Cassini and thankyou
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| Artistic visualisation of the Cassini's final moments burning up in Saturn's atmosphere (Credit: NASA) |
